This invention relates to an apparatus for introducing slivers into a fiber processing machine, particularly a regulated draw frame. The slivers are withdrawn from a plurality of coiler cans by means of driven supply rolls mounted on a creel. The slivers are introduced into a driven draw unit of the draw frame. At least two electric drive motors are provided, whose rpm may be set.
An apparatus of the above-outlined type is described, for example, in German Patent No. 198 09 875 to which corresponds U.S. Pat. No. 6,170,125.
A separate, rpm-controlled drive motor is associated with each supply roll mounted on the creel of draw frame, thus permitting an individual setting of the circumferential speed of the supply rolls.
It is an object of the invention to provide an improved apparatus of the above-outlined type with which load-dependent rpm deviations may be eliminated or compensated for in a simple manner.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the apparatus for introducing a plurality of slivers simultaneously to a sliver processing machine includes an arrangement for withdrawing the slivers from coiler cans; a creel; a plurality of supply rolls mounted on the creel and contacting the slivers; a drive, having at least one drive motor, for rotating each supply roll; a common converter connected to the drive; and an rpm setter for setting rpm""s of the drive such that the drive has an rpm essentially corresponding to a desired rpm.
While three-phase motors, because of slippage, have a load-dependent rpm characteristic, according to the invention the risks of a defective drawing process arising from such slippage is avoided. The slivers, within the creel, must not have impermissible deviations from their intake tension either with respect to one another or with respect to the unlike distances between the supply rolls and the intake roll pair mounted in the after-connected draw unit. According to the invention, despite the loads imposed on the motors, a desired rpm thereof may be fully or substantially fully achieved whereby a defective drawing of the slivers is avoided. As the driving force of the supply rolls is transferred to the slivers, material-specific frictional differences are also compensated for. While in practice the frictional force decreases from cotton (which may contain adhesive substances) through cotton/chemical fiber mixtures to pure chemical fibers (which have a smooth upper surface), by virtue of the invention, independently from the type of fiber material, a reliable and effective transfer of the driving force to the slivers is achieved. It is a particular advantage of the invention that the apparatus is inexpensive to manufacture and install.
The invention has the following additional advantageous features:
At least two drive motors are associated with the supply rolls of the draw frame creel.
With each supply roll a separate drive motor is associated.
At least one drive motor for the supply rolls and at least one drive motor for the roll pairs of the draw unit in the preliminary drafting field are provided.
The drive motor is a frequency-controlled three-phase synchronous motor or asynchronous motor. In a three-phase synchronous motor no rpm deviations are present.
The drive motor is a reluctance motor which, during acceleration, behaves like a three-phase asynchronous motor and, during normal operation, behaves like a synchronous motor so that no rpm correction is required.
The drive motor is a current rectifier-controlled direct current motor and, in such a case, the current supplying converter generates an rpm-proportional voltage.
The drive motor is a gear motor.
The drive motor is an inner rotor-type motor or an outer rotor-type motor.
The current supplying converter supplies an rpm-setting voltage of variable amplitude and frequency.
The converter is a frequency converter or a d.c. current rectifier.
The converter has a desired value transmitter such as a potentiometer operated by a control device.
An rpm transmitter, for example, a tachogenerator is provided.
If several tachogenerators are present, a mean value former is provided to which the tachogenerators are connected.
One of the drive motors or rolls, for example, a supply roll, is provided with an rpm-proportional transmitter. Such a drive motor or roll represents all the drive motors or rolls.
The rpm-proportional transmitter is connected with the converter and affects the output voltage and/or frequency of the converter such that the deviations from a desired value are maintained low.
More than one actual rpm value transmitter is provided to determine an average actual rpm of a plurality of rolls and/or drive motors. The calculated average rpm deviation affects the frequency and/or the output voltage of the current-supplying converter.
The drive motor is a direct current motor and the current-supplying converter generates an rpm-proportionate voltage which is additionally regulated by an actual rpm transmitter.
The desired rpm is formed such that it is proportional to the rpm of the input roll of the draw unit.
Drive motors having identical rpm characteristics are used for driving the supply rolls.
The rpm""s of the drive motors for the supply rolls are at least approximately identical, and means are provided for rendering the circumferential speeds of the supply rolls different from one another.
The drive motors are unregulated asynchronous motors or direct current motors supplied with current from a joint converter, and the rpm""s may be jointly set.